Shaping of non-woven batts



Jan. 4, 1966 w. coATEs ETAL 3,227,592

SHAPING OF NON-WOVEN BATTS Filed April 2, 1959 3 Sheets-Sheet 1 'LLb 1956 H. w. COATES ETAL 3,227,592

SHAPING OF NON-WOVEN BATTS Filed April 2, 1959 3 Sheets-Sheet 2 Q A x Q i 3 Z so g 31 8 T G D 'I G C) r T a- 34 Ah 1966 H. w. COATES ETAL 3,

SHAPING OF NON-WOVEN BATI'S Filed April 2, 1959 3 Sheets-Sheet 3 IQIEIQIQID IDII :QQIDI I United States Patent 3,227,592 SHAPENG 0F NQN-WOVEN BATTS Herbert W. Coates and Donald T. Dunlap, Charlotte, N.C., assignors to Celanese Corporation of America, New Yorlr, N.Y., a corporation of Delaware Filed Apr. 2, 1959, Ser. No. 893,776 18 Claims. (Cl. 156-93) This invention relates to fibrous non-woven batts or like fabrics, as well as to processes of and apparatus for imparting to such fabrics predetermined shapes and configurations in accordance with the particular intended uses for the fabrics.

Non-woven batts have been employed for filtration of fluids such as air, the batts constituting more or less randomly arranged fibers bonded together to form a stable structure. To increase the filtration efficiency it has been the practice to increase the amount of fibers in a square foot of the batt, thereby also increasing the Weight, the cost and the resistance to fluid flow. Conversely, when it has been desired to decrease the resistance to fluid flow, i.e. to decrease the pressure drop of the fluid from the input side of the filter to the out-put side, the weight of fiber per square foot has been decreased. Unfortunately, this also decreases the filtration efiiciency and at low Weights results in filters which are insufiiciently stiif or rigid to withstand normal handling and use without damage.

It is, therefore, an important object of the present invention to provide non-woven batts which can be employed as air filters without being subject to the drawbacks and disadvantages of the heretofore known batts.

It is another important object of the present invention to provide fibrous non-woven batts for use as filters for fluids such as air, in such a manner that the filters have not only the proper density but also sufiicient strength to withstand the rated air flow velocities for such units.

Still another important object of the present invention is to provide novel means for making strong, yet highly permeable air filters and other objects from non-woven fiber batts.

Concurrently it is an object of the present invention to provide novel and extremely eflicacious processes of making high strength air filters from fiber batts of the aforesaid type.

Another object of the present invention, therefore, is the provision of means for and processes of forming in non-woven fiber batts loops or convolutions of different shapes and configurations to impart to the batts the desired structural designs.

A further object of the present invention is the pro vision of means by which the aforesaid processes can be easily carried out both on relatively short lengths of batting and on relatively long, substantially endless bands or strips of batting.

Other objects and advantages of the invention will become apparent from the following detailed description and claims. In accordance with one aspect of the invention a nonwoven fibrous bonded batting is sinuously interlaced about a plurality of parallel staggered bars so as to form in the batting the desired loops, pleats or convolutions. The sodeformed batting is subjected to heat while still entwined with said bars to cause adjacent contacting loop portions to adhere to one another. Upon cooling of the batting to effect final setting in adhered condition, the bars are extracted from the batting longitudinally of the loops, whereby the formed loops are retained. The resulting article is found to have greatly enhanced rigidity over ordinary bonded batting while still retaining the necessary air permeability characteristics desired.

Patented .lan. 4, 1966 The interlacing of the batting with the aforesaid loopforming rods or bars may be carried out manually with the aid of a frame in which the rods are adapted to be retained in parallel rows by means of two oppositely located pairs of parallel slots provided in facing portions of the frame. In practice, the batt is folded back and forth across the frame about the individual bars or rods which are placed one at a time first in one of the slots and then in the other slot. Once the batt has been completely interlaced with the bars, the entire frame with bars and interlaced batting is placed for a predetermined period of time into a heating chamber and then permitted to cool, whereafter the rods and batting are removed from the frame as a unit to enable the rods to be pulled lateraliy or longitudinally out of the respective loops formed in the batting.

According to another embodiment of the present invention, the batt in the form of a relatively long band or strip is fed from the source of supply thereof, say a spool, by any suitable means, such as a pair of parallel drive rolls, into the gap between the adjacent reaches of a pair of endless chains to the outer surfaces of which are attached a plurality of transverse rods or bars by means of suitable mounting elements, the arrangement being such that the bars of one chain alternate with the bars on the other chain when located in the space or gap between the said adjacent chain reaches. Thus, the batt is entrained by the chains and folded back and forth about, i.e., interlaced with the two sets of bars therebetween, whereby the desired loops are formed. The batt may be made of cellulose acetate or similar synthetic fibers coated with a thermoplastic material. In this condition, the looped batt is conducted through a heating zone and then through a cooling zone. The loops are thus set but not bonded to the immediately adjacent loops. When the chains reach their reversal points, the bars are drawn eifectively perpendicularly out of the respective loops, whereby the adjacent loop portions remain separated from each other. A suitable adhesive is then applied to the shaped batt or fabric by spraying, brushing, dipping, or the like, and the batt is slightly compressed to cause engagement between and adhesion of the adjacent loop portions to one another. The loops are, consequently, formed substantially automatically, rather than manually as in the first described embodiment of the invention.

With respect to both of these embodiments, of course, it is possible to heat the looped batt to a temperature at which only the fibers are softened, but not the bonding agent, in order to cause the loops to be set without any bonding of the adjacent loop portions to one another. Thereafter, when the bars are withdrawn from the loops, the latter, without losing their form, are sprayed with an adhesive or bonding agent and then slightly compressed to bring the adjacent loop portions into engagement with one another so as to bond said portions to each other.

The rigidity and other mechanical strength characteristics of such batting may be increased by applying transverse bonding means to the apices of the loops thereof, for example by stitching or cross-bonding such loops along one or more lines extending transversely thereto.

The original non-woven batt may, of course, be formed in any manner desired, as by carding, cross-laying or air blowing of the fibers, which may be straight or crimped to any desired degree and the deniers of which may vary.

The foregoing and other objects, characteristics and advantages of the present invention will become more fully clear from the following detailed description thereof when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective elevational view of a frame adapted for use in a manual loop-forming operation according to the present invention;

FIG. 1a is a side elevational view of a loop-forming bar of substantially circular cross-section and adapted for use in the frame shown in FIG. 1;

FIG. 1b is an end elevational view of the loop-forming bar of FIG. 1a;

FIG. 2 is a sectional view taken along the line 2-2 in FIG. 1 and diagrammatically illustrates the interlacing of a relatively short stretch of batting with a plurality of loop-forming bars mounted in parallel rows in the frame shown in FIG. 1;

FIG. 3 is a schematic illustration of the looped batting in which the loops are not yet adhered to each other;

FIG. 4 is a similar schematic illustration of looped batting in which the adjacent loop portions are already bonded to each other;

FIG. 5 is a schematic illustration in perspective of a stretch of looped batting the loop apices of which are additionally bonded transversely to one another;

FIG. 6 is a similar illustration of a stretch of batting having transverse filaments stitched to the loop apices;

FIG. 7 is a side elevational essentially diagrammatic view of an apparatus for the continuous formation of loops in an endless band of batting according to another embodiment of the present invention;

FIG. 8 is a fragmentary detail view of the initial section of the apparatus illustrating the meshing of the loop forming bars; and

FIG. 9 is a fragmentary, perspective, elevational view of the uppermost or initial section of the apparatus shown in FIG. 7;

FIG. 10 is a schematic perspective view of an air conditioning system.

The original non-woven sheet batting is generally made of fibers of synthetic thermoplastic materials, such as cellulose acetate, nylon, and the like, alone, in admixture with each other or in admixture with non-thermoplastic fibers such as cotton, viscose, wool, sisal, asbestos, wood pulp, or the like. The batting can be prepared by carding, air blowing or cross-laying the fibers, for example, and may be provided either in relatively short sections 'of determinate length or in relatively long, substantially endless bands or strips, depending on the manner in which the loops are to be formed, as will be explained more fully hereinafter. The fibers may be coated, prior to the loop-forming operation, with an adhesive, e.g. a solution or suspension of polyvinyl acetate, etc.

Referring now more specifically to FIGS. 1 and 2, it will-be seen that for the purpose of a manual loop-forming operation to be carried out on a relatively short stretch of batting, there is provided, in accordance with the present invention, a frame or retaining member 20 having a base 21 and two upstanding end portions 22, the inner faces of the end members 22 being provided, respectively, with vertical channels or grooves 22a and 22b. The channels 22a and 221) are dimensioned to receive the opposite ends of a plurality of rods or bars 23 with which the original sheet batting is ultimately to be interlaced. As shown in FIGS. 1a and 115, each bar 23 may comprise a main section 23 of substantially circular cross-section and a pair of end sections 23" of substantially rectangular cross-section, the end sections 23" being adapted to be received non-rotatably in the channels 22a and 22b.

As can be seen from FIG. 2, in order to form loops in the sheet batting 24, a first rod or bar, designated 23a, is slid into the channels 22a, whereupon one end of the sheet 24 is held over the main section 23 of the bar 23a. A second bar, designated 23b, is now slid into the channels 22b until it rests at the bottoms thereof over the sheet 24 which is then looped about the bar 2312 and passed over the portion of the sheet resting on the bar 23a. A third bar, designated 230, is then lowered into the channels 22a and the sheet 24 looped about this bar and over that portion of the sheet looped over the bar 23b. A fourth bar, designated 23a, is now lowered into the channels 22b and the sheet looped about this bar, and this operation is continued back and forth for the entire length of the sheet 24 or to the extent permitted by the vertical dimension of the channels 22a and 22b. Thus, the batt 24 is sinuously and essentially sinusoidally twined about the bars 23.

With the batting fully interlaced with the loop-forming bars, as shown in FIG. 2, the entire unit or frame 20 is placed into a heating chamber at a temperature which will dependupon the chemical compositions of the fibers and the adhesive or bonding agent coated thereon. The temperature will be sufiicient to soften the fibers and/ or the adhesive coated onto the fibers of the batting 24, so as to cause the contacting adjacent loop portions to adhere to one another, as shown at 24a and 24b in FIG. 2. After a predetermined time interval, the unit is removed from the heating chamber and permitted to cool (if desired, it may be placed into a cooling chamber) to a temperature at which it sets, whereby the loops will be permanently retained in their adhering condition. The bars and the looped batting are then lifted bodily and as a unit out of the frame 20, whereupon the bars may be extracted laterally from the loops. The resulting fabric will then look as shown in FIG. 4.

If desired, the temperature to which the unit 20 is subjected may be insufficient to cause the required degree of adhesion between the adjacent loop portions 24a and 242:, being only high enough to ensure that the loops of the batt 24 tend to retain their sinuous shape upon being removed from the heating zone and cooled. In this case, the bars need not be extracted longitudinally or laterally of the loops, but may be extracted transversely of the respective loops, i.e., vertically with respect to the horizontal plane of the fabric. This will ensure the separation of the adjacent loop portions, and the fabric will then look as shown in FIG. 3. The looped batt is now resprayed with an adhesive, say a solution of polyvinyl acetate, whereupon the fabric is slightly compressed in either of the directions substantially transverse to the axes of the loops until the adjacent loop portions are brought into adhering contact with one another. If necessary, the so-compressed fabric or batt may be subjected to another heat treatment to finally set the adhesive or bonding medium. Ultimately, the fabric will look as shown in FIG. 4. Should it be desired to impart to the loops to be formed in the batting 24 shapes or configurations other than round, as shown in FIGS. 3 and 4, say angular or square, it will merely be necessary to employ in lieu of the round bars 23 either a plurality of triangularly shaped bars or a plurality of square or rectangularly shaped bars (neither of which are illustrated in the drawings) the cross-sections of which will be such as to provide loops or pleats of the desired shape in the batting.

Turning now to FIGS. 7, 8, and 9, the apparatus there shown is adapted for use in forming looped batting from a continuous or relatively long band of sheet batting 25. The apparatus basically comprises a pair of oppositely driven feed rolls 26 for drawing the band 25 from a spool or other source thereof and adjacent the discharge side of which is located a fabric guide 27. The width of the fabric guide 27 may be substantially coextensive with the width of the feed rolls 26 and the fabric 25. Following the fabric guide 27, there is provided a loopforming device 28 which comprises a pair of endless chains 29 and 30 each passing at one end over driven sprocket wheels 31 and 32, respectively, and at the other end over idler sprocket wheels 33 and 34, respectively. The chain 29 carries on its outer surface and at its opposite edges a plurality of mounting elements 35 and 35' laterally aligned in pairs, each pairsupporhing loop-forming bar 35 therebetween. Similarly, the. chain 30 carries on its outer surface and at its opposite edges a plurality of mounting elements 36 and 36" laterally aligned in pairs, each supporting a loop-forming bar 36" therebetween. The arrangement is such that at the adjacent reaches of the chains 29 and 30 the bars 35 are located, respectively, in the spaces between the bars 36" while the bars 36 are located in the spaces between the bars 35". Thus, the loop-forming bars 35" and 36 effectively are in meshing relationship with one another.

Arranged along the initial portion of the path of travel of the adjacent reaches of the chains 29 and 35 is a plurality of heating elements 37 defining a heating zone 38. The heating elements 37 may be steam jackets, infrared lamps or the like and may be provided with suitable control means (not shown) through which the operative temperature within the heating zone 38 may be regulated. If desired, the heating zone 38 may be enclosed in a suitable housing, as schematically indicated by the partition means 39.

Located exteriorly of the heating zone 38 and along the latter part of the path of travel of the aforesaid adjacent chain reaches is a cooling zone 40 which may be either a positive cooling chamber operated at a suitably low temperature, or merely the surrounding area in which the entire procedure is being carried out. Following the discharge end or reversal points of the chains 29 and 34} there is provided a second fabric guide 41 the function of which will become clear presently. The fabric guide 41 is slightly flared outwardly at its inlet end, as shown at 410.

In operation, the sheet or strip of batting 25 is fed from the source thereof by the feed rolls 26 into and through the fabric guide 27 and toward the initial sections or inlet end of the loop-forming device 28. As the batt reaches the region of the sprocket wheels 31 and 32, its opposite surfaces will be engaged by the bars 35 and 36", respectively, which will press the batting into the associated opposed spaces. Thus there will be formed in the batt a plurality of sucessive substantially sinuous loops or pleats due to the meshing relationship of the two sets of loop-forming bars, this meshing relationship further ensuring a positive forward feeding of the batt through the device 23. The feed rolls 26 are, of course, driven at a somewhat higher rate than the sprocket wheels 31 and 32 in order to ensure that sufficient batting is fed to the device 28 to permit the looped portions of the batting to lie with moderate tightness around the loop forming bars 35 and 36", the actual angular speeds of the rolls 26 relative to the sprocket wheels 31 and 32, i.e., the over-feed rate of the rolls 26, being determined in accordance with the sizes and types of loops or pleats to be formed.

As the looped batt enters and passes through the heating zone 38, the fibers (and binder) become soft to such an extent that, upon being resolidified by or within the cooling zone 4%, the loops are set and tend to retain their sinuous form, the arrangement being'such that no lateral adhesion between adjacent loop portions can occur. At the reversal points of the chains 29 and 30, efiectively coincident with the idler sprocket wheels 33 and 34, the rods or bars 35 and 36 are successively and alternatingly drawn out of the loops of the batt 25 in a direction substantially perpendicular to the general plane of the batt or web fabric, whereby the same will essentially look as indicated at 25a in FIG. 7.

The permanent loops now enter the fabric guide 41, the wider end 41a of which facilitates such entry and the height of which is somewhat less than the vertical dimension of the looped fabric. In this manner, a compressive force will be exerted on the loops of the batt 25, tending to widen the same and bring the adjacent loop portions into contact with one another. In this condition, the loops are resprayed with adhesive which, upon setting, causes the loops to adhere to each other, whereby the batt attains the shape and design shown in FIG. 4. The relatively long looped batt may then be cut into sections of suitable length for use as filter elements in air conditioning or warm air heating units.

From the foregoing it will be understood that the physical characteristics of the looped batt which bear on its suitability for use as a filter medium in air conditioning or warm air heating units may be varied and controlled quite extensively by a number of different factors. By way of example, by varying the shapes of the loop-forming bars and thus the shapes and configurations of the expanded or looped area of the batt, corresponding changes in the strength and bending modulus of the batt may be attained, as well as changes in the ratio of air volume to fiber volume for a given thickness of the material, whereby the resistance to air flow may be predetermined and controlled. The relatively large air voids in the batt further render the same a good insulating material, and thus the insulating Value of the batt may be changed within certain limits by varying the sizes and distribution of the said air voids. Even a simple change n the amount and type of bonding medium or adhesive employed will enable a corresponding change in the strength or stiffness of the batt to be attained.

Where it is desired to increase the strength of the batt in cases in which an optimum quantity of adhesive has already been used, reinforcing means may be provided across the opposite faces of the looped batt. This is illustrated in FIGS. 5 and 6 of the drawings.

Referring first to FIG. 5, the reinforcing means there employed are not separate and distinct from the batt 42 itself, but rather are constituted by preferably parallel zones 42a of bonded fibers extending transversely of the loops 42!). Such zones may be created by bringing into contact with one or both of the opposite faces of the batt 42, which initially is identical with that shown in FIG. 4, a plurality of hot iron rods (not shown) which soften not only the fibers of which the batt is made but also the adhesive or binder coated onto these fibers, whereby the fibers in the regions of contact of the respective iron rods are bonded to one another. It will be readily appreciated that these zones of bonded fibers will not appreciably affect the air permeability of the filter or batt while still imparting to the latter an increased resistance to buckling under the force of the air flowing therethrough.

In the embodiment of the invention according to FIG. 6, the reinforcing means are not integral parts of the batt 43 (which again is initially identical with the batt shown in FIG. 4) as are the fiber zones 42a shown in FIG. 5. Rather, the reinforcing means are constituted by a plurality of yarns 43a stitched in preferably substantially parallel courses across the loops 43b of the batt 43 at one or both of the opposite faces thereof. In either of these embodiments, of course, the reinforcing zones need not be parallel to each other, but may zig zag or be otherwise angularly oriented with respect to one another across one or both faces of the fabric.

The same effect may, of course, be attained by laminating a plurality of rods of synthetic plastic material (not shown) to the apices of the loops and substantially transversely thereto. Moreover, it is possible to vary the density and permeability of the batt per unit volume thereof, regardless of whether or not it is reinforced, by varying the deniers and staple lengths of the fibers and/ or by additionally varying the number of loops or pleats per unit linear dimension of the fabric.

The looped product, however formed, is suited for incorporation into a fluid filtering structure such as an air conditioning system as illustrated schematically in FIG. 10. As there shown a looped batt 44 is replaceably held in a frame 45 by means of corner bolts 46. The frame is positioned in the path of air blown by the fan 47 in the direction of the arrow through the conduit 48. The filtered air passes Over refrigerant coils 49 for dehumidification, after which the air is treated and distributed in conventional manner.

By way of resume, therefore, it will be seen that the process of making air filters according to the present invention basically comprises the steps of twining a plane, non-woven, synthetic thermoplastic fiber batt alternately about the individual bars (23 or 35"36") of a plurality of sets of parallel bars arranged in spaced, preferably (although not necessarily) parallel rows, to thereby form a plurality of substantially sinuous loops or pleats in the batt, heating the so-deformed batt while twined about said bars, and then cooling the batt While still twined about said bars, to effect setting of the batt in the looped condition thereof, the adjacent loop portions being in contact with and bonded to one another either during the heat treatment or subsequently thereto and either prior or subsequent to the extraction of the bars from the loops. Concurrently, of course, the apparatus according to the present invention includes means for heating the looped batt (not shown in connection with FIG. 1) and means for cooling the heated batt (also not shown in connection with FIG. 1).

While the described apparatuses are suitable for making bonded looped non-woven battings of varied composition, they are especially suited for working with battings comprising thermoplastic fibers and thermoplastic binders which are thermally set into the looped configurations during processing.

The thermoplastic fibers are preferably composed of cellulose organic acid esters although fibers of nylon, polyesters such as polyethylene terephthalate, vinylidene polymers including acrylic polymers such as acrylonitrile polymers and copolymers, vinylidene chloride polymers and copolymers and olefin polymers such as polyethylene or polypropylene, and the like, can also be employed alone, in admixture with one another or with non-thermoplastic fibers. The thermoplastic binder may comprise natural or synthetic rubber, polyvinyl acetate, or the like, and may be cured in conventional manner following formation of the looped batt by incorporating suitable curing agents in the binder composition. Alternatively, bonding of the starting batt may be effected by internal adhesion of thermoplastic fibers.

The nature of the fiber and of the bonding agent Will of course control the temperatures in loop formation. Thus with the preferred batt comprising cellulose acetate fibers bonded with polyvinyl acetate for softening both fibers and bonding agent the temperature may range from 7 about 275 to 350 F. and preferably about 300 to 325 F.

If it is desired merely to soften the bonding agent without appreciably affecting the fibers, somewhat lower temperatures may be employed, e.g. about 200 to 250 F. It is noted that these temperature values refer to the fibers or bonding agent per se, although the temperature of the air or in the oven will have to be somewhat higher.

The invention is further illustrated in the following example.

Example Using an air blowing technique there is formed from 2 inch long 35 denier staple fibers of cellulose acetate having an acetyl value of 55.0% by weight calculated as acetic acid, a non-woven batt inch thick and weighing 3.5 ounces per square yard. The batt is bonded by spraying with a polyvinyl acetate latex containing by weight of polyvinyl acetate to deposit 10 to 12% of polyvinyl acetate on the weight of the fibers. After drying to remove water, the batt is looped in the apparatus shown in FIGS. 1 and 2, held in an oven at 300 to 325 F. for 1 minute and then allowed to stand until cool. Upon removal of the forming bars the resulting looped filter is 1 inch thick and weighs 18 ounces per square yard.

A rectangular piece of the looped filter 20 by 20 inches is cut out and mounted in a frame such as shown in FIG. 10. The filter is placed in the path of 700 cubic feet of air per minute moved along by a fan to create a pressure differential of 0.08 p.s.i.g. The air is supplied with a standard test dust in accordance with the procedure of the Air Filter Institute. Over a 10 hour test period the filtration efficiency averages 70% and the pressure differ- 8. ential rises to 0.50 p.s.i.g. At the end of the test period the filter is still stiff and rigid, resilient and resistant to compression, and its thickness is the same as before the test.

In the foregoing description the direction of fluid flow has been transverse or normal to the planes defined by the surfaces of the filter. Because of the looped structure, however, fluid may flow parallel to the planes of the surfaces, i.e. it may flow longitudinally through some of the tubular passages defined by the loops and be forced to pass into other adjacent tubes in order to be discharged. While air has been disclosed as the fluid to be filtered other gases or liquids such as water, oil, gasoline, or the like, may be purified through use of the novel filters.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made in the invention without involving any departure from the spirit and scope thereof as set forth in the appended claims.

Having thus described our invention, what we desire to secure by Letters Patent is:

1. The process of making air filters from a plane, nonwoven batt, containing thermoplastic fibers comprising the steps of twining said batt alternatingly about the individual bars of a plurality of sets of parallel bars arranged in spaced rows, to thereby form a plurality of substantially sinuous loops or pleats in said batt, heating the sodeformed batt while twined about said bars, and thereafter cooling said batt while still twined about said bars, to thereby effect setting of said batt in the looped condition thereof.

2. The process of making air filters from a plane, nonwoven bonded batt containing thermoplastic fibers, comprising the steps of interlacing said batt alternatingly with the individual bars of two sets of bars arranged in substantially parallel rows to form a plurality of substantially sinuous loops in said batt, heating said batt to soften the same while said bars are in contact therewith, cooling said batt to efiect setting of said loops, and extracting said bars from said loops.

3. The process of claim 2, wherein said batt comprises cellulose acetate fibers and is heated to a temperature of about 275 to 350 F.

4. The process of claim 2, further comprising the step of subjecting the apices of said loops at at least one face of said batt to heat concentrated in a plurality of zones extending substantially transversely to said loops, to thereby effect a bonding of the fibers in each of said zones to one another, whereby separation of said loops from one another is inhibited.

5. The process of claim 2, further comprising the step of stitching at least one yard to the apices of said loops at at least one face of said batt along at least one line extending substantially transversely to said loops, to thereby affix said loops to one another and prevent separation thereof.

6. The process of claim 2, further comprising the step of interconnecting the apices of said loops at at least one face of said batt with one another along a plurality of regions extending substantially transversely to said loops, to thereby afiix said loops to one another and prevent separation thereof.

7. The process of making air filters from a plane, non. woven, thermoplastically bonded batt containing thermo' plastic fibers, comprising the steps of inter-lacing said batt alternatingly with the individual bars of two sets of bars arranged in substantially parallel rows to form a plurality of substantially sinuous loops in said batt with each loop in contact at its opposite sides with the respective adjacent loops, heating said batt to soften said fibers and the bonding agent while said bars are in contact with said batt and so as to effect adhesion of the adjacent contacting loop portions to one another, cooling said batt to effect setting of said thermoplastic fibers and said bonding 9 agent to retain said loops in their assumed and contacting condition, and extracting said bars from said loops.

8. The process of making air filters from a plane, non- Woven, thermoplastically bonded batt containing thermoplastic fibers, comprising the steps of inter-lacing said batt alternatingly with th individual bars of two sets of bars arranged in substantially parallel rows to form a plurality of substantially sinuous loops in said batt with each loop out of contact at its opposite sides with the respective adjavent loops, heating said batt while in contact with said bars to soften said fibers and the bonding agent, cooling said batt to effect setting of said loops in their laterally unadhered condition, extracting said bars from said loops in opposite directions substantially transverse to the general plane of said batt, subjecting said batt to a compressive force to bring each loop into contact at its opposite sides with the respective adjacent loops, and bonding the contacting loop portions to one another.

9. The process of making air filters from a plane band of non-woven, thermoplastically bonded batt containing thermoplastic fibers, comprising the steps of feeding said band along a first direction, pressing a plurality of staggered bars arranged in substantially parallel rows sequentially and alternatingly into contact with the opposite surfaces of said band so as to form in the latter a plurality of substantially sinuous loops, moving said bars with said looped band in engagement therewith in said first direction and through a heating zone to soften said fibers and the bonding agent, moving said bars with said looped band still in engagement therewith through a cooling zone to effect setting of said loops, extracting said bars from said loops in a second direction substantially transverse to said first direction and to the longitudinal dimensions of said loops while said band continues to move in said first direction, compressing said loops to a predetermined extent so as to bring the opposite side portions of each loop into contact with the adjacent side portions of the respective adjacent loops, and bonding the contacting loop portions to one another.

it). The process of claim 9, said bonding step comprising spraying said loops with an adhesive.

11. The process of claim 9, wherein said batt comprises cellulose acetate fibers and is heated to a temperature of about 275 to 350 F.

12. Apparatus for making air filters from a plane, nonwoven, thermoplastic fiber batt, comprising a plurality of loop-forming bars about which said batt may be twined, means for supporting said bars in spaced and staggered relationship in a plurality of substantially parallel rows, whereby said batt may be twined sinuously and in alternating sequence about the individual bars of said rows, means for heating said batt while twined about said bars and carried therewith by said supporting means, and means for cooling said batt while still twined about said bars and carried therewith by said supporting means said supporting means comprising a substantially U-shaped frame having a pair of legs and a cross member interconnecting said legs, each of said legs being provided in that face thereof facing the other leg with a first slot and with a second slot spaced therefrom and substantially parallel thereto, said first slots being substantially aligned with one another, and said second slots being substantially aligned with one another, said slots being adapted to receive the respective ends of said bars.

13. Apparatus according to claim 12, each of said legs of said frame being connected at one end thereof to said cross member and free at its other end, said first and second slots extending substantially from said one end to said other end on each of said legs.

14. Apparatus for the making of air filters from a plane, non-woven batt containing thermoplastic fibers comprising feed roll means for drawing said batt from a source thereof, first fabric guide means positioned adjacent the discharge side of said feed roll means for receiving and guiding said batt, a pair of endless chains juxtaposed to one another with their adjacent reaches being coextensive with and parallel to each other and adapted to move in the same direction, drive means operatively connected to said feed roll means and said chains for driving the same at a predetermined speed differential, a first set of mounting elements carried by one of said chains at its opposite edges, said mounting elements at each of said edges of said one chain being spaced from each other longitudinally of the latter and in alignment, respectively, with the associated mounting elements at the other edge of said one chain, a second set of mounting elements carried by the other chain at its opposite edges, said mounting elements at each of said edges of said other chain being spaced from each other longitudinally of the latter and in alignment, respectively, with the associated mounting elements at the other edge of said other chain, said mounting elements projecting outwardly from their respective chains, a plurality of elongated bars each connected to and carried by a respective one of the aligned pairs of mounting elements on each chain, said mounting elements of said one chain being staggered with respect to said mounting elements of said other chain, whereby at said adjacent reaches of said chains each of said bars on each chain is disposed intermediate an adjacent pair of bars on the other chain so as to enable the bars on said one chain and the bars on said other chain to contact the opposite surfaces of said batt in alternating sequence upon entry of said batt into the space between said adjacent chain reaches from said first fabric guide means for forming a plurality of substantially sinuous loops in said batt, heating means located along the initial part of the path of movement of said adjacent chain reaches for softening said fibers and said binder, cooling means located along the final part of the path of movement of said adjacent chain reaches for setting said loops in their assumed form, and second fabric guide means located at the reversal points of said chains for receiving the looped batt upon withdrawal of said bars therefrom and for effecting compression of said loops to bring the adjacent loop portions into contact with one another for bonding purposes.

15. Apparatus according to claim 14, said drive means being operable to drive said feed roll means at a higher speed than said chains, to facilitate moderately tight but non-stretching twining of said batt about said bars.

16. Apparatus for making air filters from a plane, nonwoven, thermoplastic fiber batt, comprising a plurality of loop-forming bars about which said batt may be twined, means for supporting said bars in spaced and staggered relationship in a plurality of substantially parallel rows, whereby said batt may be twined sinuously and in alternating sequence about the individual bars of said rows, means for heating said batt while twined about said bars and carried therewith by said supporting means, and means for cooling said batt while still twined about said bars and carried therewith by said supporting means, said supporting means comprising a pair of endless, driven chains the adjacent reaches of which face and are parallel to one another while moving in the same direction and means for receiving said batt positioned adjacent the point where the chains move out of parallel relationship, and effecting compression of the loops of said non-woven batt to bring the adjacent loop portions into contact with one another for bonding purposes, each of said chains using provided adjacent its opposite side edges with a plurality of mounting elements spaced from one another longitudinally of the respective chain and projecting outwardly relative to the same, each of said mounting elements at one edge of each chain being aligned with a corresponding mounting element at the opposite edge of the same chain, said bars being connected to corresponding pairs of aligned mounting elements, respectively.

17. Apparatus according to claim 16, said pairs of mounting elements on one of said chains being staggered with respect to the pairs of mounting elements on the other chain, whereby at said adjacent reaches of said chains each bar carried by each chain is disposed intermediate an adjacent pair of bars carried by the other chain.

18. Apparatus according to claim 17, said heating means being positioned along the initial part of the path of movement of said adjacent chain reaches, said cooling means being positioned along the final part of the path of movement of said adjacent chain reaches.

References Eited by the Examiner UNITED STATES PATENTS 1,263,577 4/ 1918 Lochman. 1,506,955 9/ 1924 Thero. 1,989,690 2/1935 Hcldenbrand et a1. 2,075,735 3/ 1937 Loomis. 2,464,301 3/ 1949 Francis. 2,480,316 8/1949 Blair et a1 154-3305 2,513,777 7/1950 Andre 154-30 Stevens 183-45 Swayze et a1. Allen 18345 Hemmi. Gordon.

Larson 15430 Wilhelm et al 15 6324 Allen et a1. Allan. Hoffman.

Germany.

15 EARL M. BERGERT, Primary Examiner.

C. T. KRAFFT, W. I. VAN BALEN, M. E. ROGERS,

H. B. THORNTON, Assistant Examiners. 

2. THE PROCESS OF MAKING AIR FILTERS FROM A PLANE, NONWOVEN BONDED BATT CONTAINING THERMOPLASTIC FIBERS, COMPRISING THE STEPS OF INTERLACING SAID BATT ALTERNATINGLY WITH THE INDIVIDUAL BARS OF TWO SETS OF BARS ARRANGED IN SUBSTANTIALLY PARALLEL ROWS TO FORM A PLURALITY OF SUBSTANTIALLY SINUOUS LOOPS IN SAID BATT, HEATING SAID BATT TO SOFTEN THE SAME WHILE SAID BARS ARE IN CONTACT THEREWITH, COOLING SAID BATT TO EFFECT SETTING OF SAID LOOPS, AND EXTRACTING SAID BARS FROM SAID LOOPS.
 5. THE PROCESS OF CLAIM 2, FURTHER COMPRISING THE STEP OF STITCHING AT LEAST ONE YARD TO THE APICES OF SAID LOOPS AT AT LEAST ONE FACE OF SAID BATT ALONG AT LEAST ONE LINE EXTENDING SUBSTANTIALLY TRANSVERSELY TO SAID LOOPS, TO THEREBY AFFIX SAID LOOPS TO ONE ANOTHER AND PREVENT SEPARATION THEREOF. 